Many animals are known to seek out plants and other non-food substances for medicinal reasons. Parrots, for instance, have been documented eating clay to absorb toxins in their gut. Brown bears have been witnessed making a paste of osha roots and saliva, which repels insects when rubbed in their fur. Dogs often eat grass, which helps makes them vomit when they have an upset stomach. 

But all of these examples involve vertebrates. Evidence of medicinal plants use by invertebrates remains scant, which is why researchers were surprised to recently find evidence that bumblebees infected by parasites seem to seek out flowers with nicotine in the nectar, reports Science Daily.

This behavior is particularly fascinating because while nicotine can slow the progression of disease in bumblebees infected with certain parasites, it can nevertheless be harmful to healthy bumblebees. So clearly the bees would not seek it out except as an emergency medicine, similar to how human doctors use chemotherapy to treat cancer.

Researchers from Queen Mary University of London and Royal Holloway, University of London found that bumblebees infected with the gut parasite Crithidia bombi were more likely to seek out nicotine-laced nectar than healthy bumblebees were. Furthermore, bees that took the nicotine were more likely to have delayed infection rates. They also showed lower levels of parasites in general, indicating that the nicotine was effective at staving off illness. 

But as with healthy bumblebees that consume nicotine, the bees that took the substance still suffered from other negative side effects. For instance, the nicotine suppressed their appetite much in the same way that it does in humans who smoke. As a result, bumblebees that self-medicated did not actually live any longer than infected bees that avoided the nicotine. But it's possible that the nicotine treatment at least helped the bumblebees to better manage their illness, and thus live more productive lives.

"Given the stresses placed on worldwide bee populations by disease, understanding how the bees themselves fight infection is key," said Dr. David Baracchi, co-author of the study.

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